Making his first start of the year, the 48-year-old Mickelson shot a bogey-free 6-under 66 on the Stadium Course at PGA West to get to 22-under 194. He topped the leaderboard for the third straight day after matching his career-low score with an opening 60 at La Quinta Country Club and shooting a 68 on Friday on PGA West’s Nicklaus Tournament Course.
The tournament winner in 2002 and 2004, Lefty rolled in a 35-foot birdie putt on the par-3 13th and added a 15-footer on the par-4 14th. After missing a 9-foot try on the par-5 16th to spoil an up-and-down bid from the deep greenside bunker, he ran in a 25-footer on the island green, par-3 17th called Alcatraz.
Canadian Adam Hadwin was second after a 65 on the Nicklaus layout.
Mickelson is making his first tour start since early October and first competitive appearance since beating Tiger Woods in Las Vegas in November in a made-for-TV event. The Hall of Famer won the World Golf Championships-Mexico Championship last year for his 43rd PGA Tour title and first since the 2013 British Open.